1. Field of the Invention
The present invention relates to an electronic musical instrument with a touch response function which is capable of varying a volume and a timbre of a musical tone in accordance with initial or after touch data representing a velocity and/or a pressure of an operated play input, such as keys, strings and blowing.
2. Description of the Related Art
There has been an electronic musical instrument of the type in which the touch data entered is compared with a prefixed touch split point or a touch split point set by a player, and a waveform (fundamental waveform) of a musical tone is set up on the basis of the result of the comparison (see FIG. 1). For example, when the entered touch data is larger than the preset touch split point, a waveform sampled for large touch data (referred to as a strong-touch tone waveform) is selected for the tone waveform. A volume of the tone is based on the touch data. Incidentally, a waveform sampled when the touch data is smaller than the touch split point is called a weak-touch tone waveform. A typical example of the musical instrument of this type is disclosed in U.S. patent application No. 760,290, filed on July 29, 1985, and issued as U.S. Pat. No. 4,681,008. The approach of the touch data-touch split point comparison shown in FIG. 1 can readily make the function to vary a timber of a tone in accordance with the touch data. When the musical instrument designed on the basis of the above approach is continuously played using the touch data in the vicinity of the touch split point, a timber of a tone rapidly varies. The rapidly varying timbre makes listeners feel unnaturally.
To cope with the unnatural feeling, there is proposed another approach, called a velocity cross fade, in which a ratio of the strong-touch tone waveform and the weak-touch tone waveform that are to be mixed is gradually changed in the vicinity of a waveform change point. A typical example of the musical instrument designed based on this approach is DIGITAL WAVE FILTERING SAMPLER TX16W manufactured by Yamaha Co. The musical instrument employs two sound source lines. The strong-touch tone waveform and the weak-touch tone waveform are respectively assigned to the sound source lines. When the touch data is small, viz., a velocity of a play input is slow, one of the sound source lines provides a musical tone with a timbre based on the weak-touch tone waveform configured by a .beta. touch curve (see FIG. 2). When the touch data becomes large, the other sound source line provides a musical tone with a timbre based on the strong-touch tone waveform configured by an .alpha. touch curve. In the velocity fade interval, a tone with a timbre based on the weak-touch tone waveform is mixed with a tone with a timbre based on the strong-touch tone waveform in a cross fade mode, and is sounded. A mixing ratio of those waveforms is varied for musical tone formation. This approach indeed succeeded in solving the unnatural feeling problem due to a rapid variation of the timbre. However, the approach involves another problem when a tone is detuned by staggering the frequencies of the tones of the sound source lines, with an intention to give the tone beats and something deep. The detune is effective only in the cross fade interval where the sound source lines concurrently provide the tone waveforms of different frequencies. As a whole, the detune effect is indistinctive.
An additional approach to vary the volume and the timbre of a tone in accordance with the touch data has been known. Electronic musical instruments implementing the approach is disclosed in U.S. patent application No. 199,166, filed on May 26, 1988, and issued as U.S. Pat. No. 4,875,400. The musical instrument is configured as shown in FIG. 3. In the figure, a sinusoidal waveform as a fundamental waveform of a tone is read from a waveform memory 1. 0n the basis of the sinusoidal waveform data, four lines individually produce four sinusoidal wave signals 2-1 to 2-4 of different pitches which are related to one another in an overtone fashion, for example. Touch controllers 3-1 to 3-4 touch controls o level controls the sinusoidal wave signals 2-1 to 2-4 by using different touch response data (touch curve) defining the relation of the touch data and the sounding level. The sinusoidal wave signals of four lines that are level controlled in accordance with the touch response data, are added together by an adder 4, thereby to form a composite musical tone waveform. The composite waveform is applied to an envelope controller 5. Controller 5 varies the composite waveform with respect to time in accordance with an envelope supplied from an envelope generator (not shown), resulting in a musical tone.
In this type of the electronic musical instrument, it is only the same tone waveform that can be set to the four lines. Therefore, even if the different touch controls are applied to the four lines, it is impossible to obtain such a musical tone that is generated only when a play input of a strong touch, for example, occurs. A variation in a timbre of the resultant tone is poor.